The invention relates to a feed roller for guiding a tree trunk advantageously in a timber harvesting machine, the feed roller comprising a drive wheel, at least one transmission means arranged at the outer circumference of and controlled by the drive wheel, the transmission means having engagement plates provided with gripping means.
This apparatus is in general used for feeding a cut tree trunk into the timber harvester for delimbing.
In the Nordic countries, so-called feller heads are currently in general use in timber harvesting, previously these apparatuses were also known as single-grip harvesters. The apparatus has means for felling, delimbing and cutting a tree. When working with this kind of feller head, the tree is gripped and felled with felling means of the apparatus. After felling, the tree is in general delimbed by feeding the tree trunk through a ring formed by various knife-like blades, whereby the branches become detached from the trunk when hitting the blades. In order that delimbing were sufficiently efficient, the feller head must, however, get as firm a hold as possible on the surface of the trunk when it is fed towards the blades of the apparatus. On the other hand, in order to prevent wood from being damaged by means pressing the trunk, when the trunk is being fed through the feller head, the means pressing the trunk must provide an even contact surface with wood. In addition, the even contact surface must be provided for a variety of trunk diameters.
For the above reasons, various anti-skid solutions have been developed which equalize surface pressures and thus damage wood less, and adapt to the surface better. These kinds of solutions are disclosed, for instance, in Finnish Patents 55,103, 82,898, 84,445 and 97,785 and in Finnish Patent Applications 931062, 942708, 952262 and in Finnish Utility Model 1150.
In various anti-skid solutions which equalize surface pressures, separate anti-skid devices have conventionally been attached to a rubber coated wheel. Hence the anti-skid devices yield when coming into contact with a wood surface by sinking into the rubber coating of the wheel and thus equalize the pressure exerted on wood. In these apparatuses, various chains, nets or plates with optional welded gripping means, are generally used as anti-skid devices.
The currently used rubber wheels have, however, considerable drawbacks, which have not been solved so far. The rubber coating on a conventional wheel absorbs, for example, some of the feeding energy exerted on the tree trunk, and consequently more power is needed to drive the wheel. However, increased power leads to warming up of the wheel and the rubber coating thereon. Warming up is disadvantageous, since it leads to changes in the external dimensions of the wheel, which in turn causes constant inaccuracy in measuring timber which is handled with the feller head.
The warming up of the conventional rubber coated wheel also causes softening in the rubber coating, causing the mechanic anti-skid devices arranged on the wheel to sink more readily into the rubber and wear the rubber coating rapidly, which shortens the wheel's service life. Thus the conventional rubber coated wheel has to be re-coated often, which on one hand is expensive and on the other hand causes disadvantageous down-time in the use of the timber harvesting machine.